The present invention relates to an analog circuit, an electronic instrument, and an operational amplifier.
The noise of a transistor forming an analog circuit is classified as thermal noise and flicker noise. Thermal noise predominantly occurs in a high frequency band and is proportional to the absolute temperature. Flicker noise predominantly occurs in a low frequency band. The noise level of flicker noise increases as the signal frequency decreases.
In analog circuits such as a radio-controlled clock receiver device and a gyrosensor detection device, a frequency is converted using a mixer or the like (e.g., JP-A-3-226620). Specifically, the frequency of a carrier signal is converted into the frequency of a desired signal, for example. Therefore, a high signal frequency and a low signal frequency exist in a mixed state as the small-amplitude amplification target of an operational amplifier forming an analog circuit.
In known analog circuits such as a radio-controlled clock receiver device and a gyrosensor detection device, an operational amplifier has not been optimally sized taking such a difference in signal frequency into consideration. Moreover, a reduction in noise and power consumption in combination has not been taken into consideration.